Paint Calculator
Wall area is 2 × (length + width) × height. Doors subtract 20 ft² each. Windows subtract 15 ft² each. Gallons are net area times coats divided by coverage, then rounded up to buy. Estimate only.
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How to estimate gallons of paint
- Enter room length, width, and wall height in feet, meters, or inches.
- Set coats and the coverage printed on the can, in square feet per gallon.
- Count doors and windows. Each door removes 20 ft². Each window removes 15 ft².
- Read paintable area and gallons, then the buy count rounded up. Confirm with the label. Estimate only.
Wall paint quantity
Rectangular room walls minus openings
| Wall area | 2 × (L + W) × H |
|---|---|
| Door | 20 ft² each |
| Window | 15 ft² each |
| Gallons | net × coats / coverage |
| Buy | ceil(gallons) |
| Advice | Estimate only. Not a specification or code approval. |
How wall paint gallons are computed
Dimensions convert to feet. Four walls use 2(L+W)H. Openings subtract 20 ft² per door and 15 ft² per window, not below zero. Gallons divide net area times coats by coverage. Buy rounds up.
Coverage, coats, and openings
Coverage is a can rating, often near 350 ft² per gallon on a smooth wall. Texture, primer, and color change that. Floor area without height is square footage. Tile count is the tile calculator. A slab pour is concrete.
Estimate only
Ceilings, trim, and cabinets are not in the wall formula. The page does not pick sheen or VOC. Not code approval.
Use cases
A bedroom recut, comparing one coat versus two, or shrinking gallons after counting two windows. Odd niches need extra area you add mentally.
Limits
Length, width, height, coats, and coverage must be greater than 0. Door and window counts cannot be negative. CZNull does not receive the numbers.